Generally, a brake system of automotive vehicle restricts the rotation of wheels. The brake force stops or restricts the speed of the car.
The general brake system of vehicle, as shown in FIG. 1, has a mastercylinder 10 generating hydraulic pressure by stepping on the brake pedal 12, a brake shoe 14 or a calliper 16 which contacts with a drum 18 or a disk 20 of the car wheel and generates friction force, and a wheel cylinder 21 actuated by the hydraulic oil force from the master cylinder 10 and pushing the brake shoe 14 or the calliper 16 to the drum 18 or the disk 20.
Between the brake pedal 12 and the master cylinder 10 is positioned a booster 22 which increases the stepping force of the foot pedal. Therefore, the high hydraulic oil force can be generated by the stepping force of the brake pedal through the master cylinder 10 and the booster 22.
The hydraulic oil force of the booster 22 is transferred to the brake shoe 14 or the calliper 16, and friction force is generated between the brake shoe 14 or the calliper 16 and the drum 18 or the disk 20, to stop or reduce the revolution speed of the car wheel.
If different loads are applied crosswise along a car between the side wheels of the car, a biased brake forced is generated, particularly when a much larger load is applied to one of the side wheels. That is, one side wheel when less load is applied is more locked than the other side wheel by the hydraulic force supplied from the brake system. Therefore, for prohibiting the biased braking force, a hydraulic brake force regulating device is widely used in an automotive vehicle.
The prior brake hydraulic force regulating device as shown in FIG. 2, is composed of a spring lever 22 which is mounted on one side of the center portion of an axle housing 24, and a control spring 26 which is mounted between the axle housing 24 and the side frame 28 of the car body.
When the biased load is applied to the axle housing 24, the axle housing 24 is inclined to one side of the car body and the control spring 26 senses the inclination of the car body.
An operating lever 30 is provided on the control spring 26 and a hydraulic force regulating valve 32 being controlled by the operating lever 30 is provided on the oil line 34 through which the hydraulic brake oil is transferred from the master cylinder 10 to the wheel cylinder 21
If a biased load is applied on both side wheels, the one end of the axle housing 24 where less load is applied is raised upward. At this time, the operating lever 30 is actuated by the spring lever 22 and the control spring 26, and the hydraulic brake force regulating valve 32 is controlled by the operating lever 30 so that more brake hydraulic oil is transferred to the brake wheel cylinder where more load is applied.
Therefore, when a biased load is applied both wheels are braked by the same brake force. One wheel of the side wheels is not locked and biased brake force is prohibited, and safety braking can be expected.
However, since the prior brake system comprising the control spring 26 and the hydraulic brake regulating valve 32 is a mechanical mechanism, the exact operation of the hydraulic brake regulating valve can not be ensured.